{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SY8540-8","brand":"Siemens","brandSlug":"siemens","productSlug":"5SY8540-8","canonicalUrl":"https://aoctrl.com/siemens/5SY8540-8","factsUrl":"https://aoctrl.com/api/mcp/products/5SY8540-8","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SY8540-8 miniature circuit breaker, D characteristic, 40 A, 25 kA per IEC 60947-2, 2-pole (1P+N), 2 MW, IP20.","salesMarkdown":"The Siemens 5SY8540-8 is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, rated 40 A at 230/400 V AC, and a 25 kA breaking capacity per IEC 60947-2. This is a 2-pole (1P+N) unit with neutral switching, so it opens both phase and neutral on a fault. That matters in applications where the neutral must be positively isolated — not just switched — for maintenance or safety. ## Deployment context and environmental limits Vibration resistance per IEC 60068-2-6 (±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz) confirms it survives on machinery or in mobile equipment. The sealable design allows a lock or tag to prevent unauthorized operation — useful for lockout/tagout programs. ## Integration: what fits where Any mounting position is permitted. ## Temperature derating — the number that matters for real loads At 40 °C the breaker carries its full 40 A. At 50 °C it derates to 38.76 A; at 55 °C to 37.48 A. The humidity limits (95% at 55 °C, 55% at 70 °C, 35% at 75 °C) are typical for indoor industrial environments; condensation is not expected.","metaTitle":"Siemens 5SY8540-8 SENTRON MCB, D-curve, 40 A, 25 kA, 2-pole","metaDescription":"Siemens 5SY8540-8 SENTRON miniature circuit breaker, 40 A rated, D tripping characteristic, 25 kA breaking capacity per IEC 60947-2. Active production. Sourced to order against RFQ","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["1-Pole MCB (DIN Rail)"],"specifications":{"Depth":"76 mm","Width":"36 mm","title":"5SY8540-8","Height":"90 mm","Maximum":"75 °C","Minimum":"-40 °C","Sealable":"Yes","description":"Miniature circuit breaker 230 V D=70 mm 25 kA according to EN 60947-2, 1P+N, D40","Halogen-Free":"Yes","Silicon-Free":"Yes","Design Of Pole":"1P+N","Number Of Poles":"2","lifecycle_stage":"current","Fastening Method":"Quick assembly system","Mounting Position":"any","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Degree Of Pollution":"3","Product Designation":"Miniature circuit breaker","at AC / rated value":"40 A","protection class IP":"IP20, with connected conductors","Overvoltage Category":"III","Combined Terminal Top":"Yes","according to EN 61346-2":"F","at 45 °C / rated value":"40 A","at 50 °C / rated value":"38.76 A","at 55 °C / rated value":"37.48 A","Combined Terminal Bottom":"Yes","according to IEC 81346-2":"F","Suitability For Operation":"Mechanical engineering / industry","Neutral Conductor Switching":"Yes","Number Of Modular Width Units":"2","Tripping Characteristic Class":"D","Position / Of Power Supply Cord":"Any","according to IEC 60947-2 / rated value":"25 kA","Influence Of The Surrounding Temperature":"max. 95% to 55°C, max. 55% to 70°C, max. 35% to 75°C","Type Of Voltage / Of The Operating Voltage":"AC","Value Range / Of The Supply Voltage Frequency":"50/60 Hz","at DC / according to IEC 60947-2 / rated value":"15 kA","operating voltage / at DC / rated value / maximum":"72 V","vibration resistance / according to IEC 60068-2-6":"±1mm at 5 to 25Hz; 50m/s² at 25 to 150Hz","with single-phase operation / at AC / rated value":"250 V","Mechanical Service Life (Switching Cycles) / Typical":"10 000"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/9d390e605455155a8b42710f1e504d2a.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=143495&mlfb=5SY8540-8"},"ai":{"faq":[{"question":"What is the breaking capacity of the 5SY8540-8?","answer":"25 kA per IEC 60947-2 at 400 V AC. At DC (up to 72 V) it is rated 15 kA per the same standard."},{"question":"Where can I buy the 5SY8540-8?","answer":"We supply this part to order against an RFQ. Availability and current pricing are confirmed at quote time through independent distribution. Submit an RFQ for a firm price and lead time."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SY8540-8","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/5SY8540-8 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}